Penn was in peak form under the guidance of the Marinovich brothers, who helped prepare him for back-to-back lightweight title bouts against Diego Sanchez and Kenny Florian. The two sides parted ways midway through training camp for Penn's first fight with Frankie Edgar.

Penn went on to lose a controversial decision and the UFC lightweight title, but his work with the Marinovich brothers helped him go five hard rounds against one of the most conditioned fighters in all of MMA.

Despite his overwhelming talent, Penn has struggled throughout his entire career with conditioning, which has prompted fans and media to always question his motivation. The Marinovich brothers were somehow able to dig deep and bring out the best in him.

If Penn decides to keep fighting, it'll be interesting to see if he returns to the lightweight division. He looked completely undersized in recent losses to Rory MacDonald and Nick Diaz.

There certainly isn't any shame in losing back-to-back fights to Edgar, who some still consider to be one of the best pound-for-pound fighters in the world. Penn would immediately fit right into the mix for the UFC title at 155 pounds.

The exciting news will undoubtedly be met with strong skepticism. Penn hasn't even won a fight in over two years, but it's hard not to be intrigued by the possibility of him returning to lightweight under the tutelage of the Marinovich brothers.